Patent GB-501987-A (GB)
Title: Improvements in or relating to colour photography
IPC: G03C7/26
Filed: 1937-09-10
Abstract: 501,987. Colour photography. BUTEMENT, C., and DUFAY-CHROMEX, Ltd. Sept: 10, 1937, No. 24771. [Class 98 (ii)] Material for producing coloured images comprises a support carrying a silver halide emulsion layer containing nickel carbonate or nickel hydroxide. After exposure, development, and bleaching of the silver halide, the nickel carbonate or hydroxide is converted into a nickel compound which reacts with the silver-compounds produced by bleaching the silver image to provide a reaction product which is coloured or may, by further treatment, be converted into a coloured product. The silver image may be bleached to silver ferrocyanide, the nickel carbonate or hydroxide converted to nickel chloride, the nickel chloride allowed to react with the silver ferrocyanide to produce nickel ferrocyanide, and the latter converted to nickel dimethylglyoxime by treatment with dimethyiglyoxiine. Two-layer material comprises two differently coloured sensitized silver halide emulsion layers, one of which contains nickel carbonate or nickel hydroxide and the other an insoluble ferric compound such as ferric hydroxide or ferric carbonate. Ferric chloride is produced in the latter by treatment with hydrochloric acid and reacts with the silver ferrocyanide to produco ferric ferrocyanide. Three-layer material comprises on a support a bottom redsensitized silver halide emulsion containing acid-magenta and also ferric hydroxide or carbonate, a middle green-sensitized emulsion containing auramine and nickel hydroxide or carbonate, and a top blue-sensitized emulsion containing lead carbonate. The dyes may alternatively be in separate layers, which may contain precipitating agents for metallic compounds in contiguous layers. After exposure, the material is developed and fixed, and the silver image is bleached to silver ferrocyanide. The ferric compound is converted to blue ferric ferrocyanide, the nickel compound to magenta nickel dimethylglyoxime, and the lead carbonate to yellow lead chromate by conversion to lead chloride and subsequent treatment with potassium chromate. The material may be used for camera exposure or printing. A multicolour screen negative may be printed on the material. The red-sensitizer may be Dicyanin or Pinacyanol, and the green-sensitizer Pinaverdol or Erythrosin. The solution for converting the nickel ferrocyanide to nickeldimethyloxime comprises dimethylglyoxime, triethanolamine and water. The print is finally cleared in a À1 per cent acetic acid bath, fixed in hypo, transferred to a permanent base and the original paper support stripped off. The printing light may be obtained from a discharge lamp of the kind known under the Registered Trade Mark " Osira," which gives the green and blue mercury lines and the red cadmium line. The light is filtered with a didymium chloride liquid filter or a glass filter, and may be used to illuminate diffusely the original and the copy material or successive exposures may be made using trichromatic filters. A rotating filter disc may be arranged between the light filter and the original. The top blue-sensitive layer may contain no added metal salt, the silver image being toned to yellow lead chromate or by treatment with mercuric potassium iodide to yellow mercuric iodide. The red-sensitized layer containing ferric hydroxide and the green-sensitized layer containing nickel carbonate may be on the same or opposite sides of one support, and the blue-sensitive layer on another support. The emulsions are preferably silver chloride emulsions, but a silver bromide' emulsion may be used for the blue-sensitive layer. Prints may be made from a multicolour screen diapositive and developed by reversal, or may be made from subtractive originals. The process may be applied to the printing of kinematograph films. The material according to the invention may be exposed in a camera and developed as a negative, and printed by contact or projection on to similar material. Specification 334,004, [Class 98 (ii)], is referred to.